Location : Timmins, Ontario, Canada.
Products : Silver & Gold.
Ore Type: The Dome Mountain area has numerous gold bearing quartz-sulphide veins.
El Chino Copper Mine
El Chino Copper Mine
Location: Santa Rita, New Mexico, United States.
Products: Copper Deposit.
Ore Type: Porphyry copper deposit with adjacent copper skarn deposits.
Host rocks: The predominant oxide copper mineral is chrysocolla. Chalcocite is the most important secondary copper sulfide mineral, and chalcopyrite and molybdenite the dominant primary sulfides.
Geological setting: The Cobre Mountains are composed of Proterozoic metamorphic and igneous rocks covered by about 3800 to 4800 feet of Paleozoic to Mesozoic sedimentary rocks. Cretaceous diorite to quartz diorite sills subsequently intruded these older rocks. Shortly thereafter, mafic to intermediate composition dikes and other intrusive bodies were emplaced and 2000 feet of intermediate composition lavas and breccias were erupted onto the surface. Next, the large granodioritic plutons at Chino and at Hanover-Fierro to the north were intruded. The last stage of intrusive activity in this area was the emplacement of rhyolitic dikes. The multiple intrusions locally domed and folded the older Paleozoic and Cretaceous strata.
Mineralization: Porphyry copper deposit are low-grade (<0.8%) disseminated deposits of copper found in and around small intrusive bodies composed of porhyritic diorite, granodiorite, monzonite or quartz monzonite (McLemore, 2008). The small plutons (also called stocks) are often shallowly emplaced at depth within 1 to 6 km of the earth's surface. The copper occurs within breccia or in networks of fractures, both in the porphyritic intrusion and in the adjoining country rocks.
Location: Orange, New South Wales,is one of three gold mines Newcrest currently operates in Australia.
Products: Copper & Gold. A series of large underground and open-cut gold and copper mines
Ore Minerals: Ore minerals are native gold, chalcopyrite and bornite, mostly occurring within veins, but also disseminated. Magnetite is a major accessory mineral in veins. Hydrothermal alteration associated with the strongest mineralisation is potassic: orthoclase, albite, actinolite, magnetite, biotite. This is overprinted by later propylitic assemblages: epidote, chlorite, Fe-carbonate, calcite, hematite dusting.
Geological setting: The Cadia deposits are part of a Late Ordovician – Early Silurian porphyry alteration-mineralisation system that extends over an area of at least 6 X 2 km within the Ordovician Molong Volcanic Belt of the Palaeozoic Lachlan Fold Belt (Newcrest Mining Staff, 1997). The Molong Volcanic Belt comprises a suite of intermediate to basic volcanics, volcaniclastics, comagmatic intrusions, and limestones. The suite is probably part of a subduction-related island arc disrupted by later tectonism (Glen et al, 1997). In the Cadia area the volcanics and intrusions are shoshonitic (Blevin, 1998).
Mineralization: Sheeted quartz vein, stockwork quartz vein, disseminated and skarn, all of which are genetically related to a relatively small (3 X 1.5 km in outcrop) composite intrusion of predominantly monzonitic composition, with a monzodioritic to dioritic rind (Cadia Hill Monzonite). The Cadia Hill Monzonite intruded Forest Reefs Volcanics (volcaniclastics, lavas, subvolcanic intrusions, and minor limestone) and Weemalla Formation (siltstone, mudstone, minor volcaniclastics). Emplacement of the Cadia Hill Monzonite was probably facilitated and localised by the development of a major north-west (NW) to south-east (SE) trending dilational structural zone, which is well evident in magnetic data.
Bonikro Gold Mine
|Bonikro Gold Mine|
Location: Bonikro, Côte d’Ivoire.
Ore Type: Disseminated
Geological Settings & Mineralization: The Bonikro deposit is hosted primarily within a small granodiroite intrusion. Mineralisation extends into surrounding basalts to the south, and is controlled along a moderately dipping shear zone. Gold occurs associated with quartz and pyrite, with the highest gold grades occurring around the intersection of the shear and the granodiorite. Overall, the deposit has an average grade below 2g/t gold.
For Satellite View and Data Sheet Here
Sunrise Dam Gold Mine
|Sunrise Dam Gold Mine|
Location: Laverton, Western Australia.
Geological Settings: The deposit is hosted by the Archaean Norseman-Wiluna belt, in the Eastern Goldfields Province of the Yilgarn Craton. The deposit falls within the structurally complex Laverton Domain, which is characterized by tight folding and thrusting. A number of other Au deposits lie within or near the margins of the Laverton Domain, including Laverton, Granny Smith (this volume), Red October (this volume), Childe Harold, Lancefield and Keringal. Most of these deposits are hosted by metasedimentary rocks, a distinctive feature of the Laverton region relative to other parts of the Yilgarn Craton.
Host Rocks: The host rocks are shallow-dipping interbedded Archaean metasedimentary, metavolcaniclastic and felsic to intermediate metavolcanic rocks (Newton et al., 1998). The metavolcaniclastic rocks are interbedded with BIF. In general, they are thick, bedded to massive and fine upwards. The BIF units are typically 2-10 m thick and commonly grade into magnetite-rich tuffs. A 20-40 m thick mafic intrusive postdates the metavolcaniclastic sequence on the western side of Cleo. Quartzfeldspar porphyries also intrude the sequence at both Cleo and Sunrise and, at Cleo, post-date the mafic intrusive.
Mineralization: The Sunrise Shear, within the Archaean rocks, controls geometry of the mineralization and is thought to have been the main conduit for Au-bearing hydrothermal fluids (Newton et al., 1998). Pyrite replacement of BIF accounts for most of the primary mineralization and is well developed where the shear zones, parallel to bedding, follow the contact of BIF with less competent units. Gold is also associated with quartzankerite- pyrite veins and pervasive ankerite-silica-sericite-pyrite alteration of intermediate volcaniclastic host rocks. Thin quartz-carbonate veins also host Au, but are mostly located in the Sunrise part of the deposit. Supergene mineralization has developed in the weathered bedrock and in transported cover in the eastern part of the study area.
Yanacocha Gold Mine
Yanacocha Gold Mine
Location: Cajamarca, Peru.
It is the largest gold mine in Latin America, and The second largest gold mine in the world, producing over US$7 billion worth of gold to date.
Deposit Type: High sulfidation- type epithermal gold deposits.
Geological Settings & Mineralization:
The high-sulfidation epithermal gold deposits are hosted by volcanic rocks that occur at the southern terminus of the northern Peruvian volcanic belt, a continuous sequence of a north-northwest trending Miocene-Pliocene suite of bimodal andesite to rhyolite volcanic rocks that extend into southern Ecuador. In the Yanacocha district, the volcanic pile has been subdivided into three groups: (1) the lower andesite sequence, consisting of an intercalated sequence of block and ash flow tuffs, flow sequences with rare, associated flow domes, and an upper zone dominated by ignimbrites and fine-grained, laminated epiclastic sequences that show a transition into the overlying Yanacocha pyroclastic sequence; (2) the Yanacocha pyroclastic sequence, a variable sequence of lithic to lithic crystal tuffs, extensively altered in the central portion of the district and primary host to the majority of gold deposits within the district; (3) the upper andesite-dacite sequence, consisting of intercalated units of andesite to dacite flows, dominated by multiple flow dome complexes in its upper portion. Ar-Ar age dating within the district has yielded ages ranging from 19 Ma (basal lower andesite) to >12 Ma (upper andesite sequence). The entire volcanic pile has been crosscut by multiple phases of phreatic (vapor phase dominant), phreatomagmatic (intrusive component) and hydrothermal breccias, and intruded by multiple late-stage phases of andesite dikes and dacite to quartz dacite plugs, dikes and stocks (10–8 Ma), the latter of which are associated with shallow Au-Cu porphyry-style mineralization that underlies the high-sulfidation epithermal deposits.
|Schematic map showing the geology of western Peru and general location of the Yanacocha mining district.|
Grasberg Gold & Copper Mine
It is the largest gold mine and the third largest copper mine in the world.
|Grasberg Gold & Copper Mine|
Location: Papua, Indonesia.
Products: Gold & Copper.
Deposit Type: Porphyry deposits associated with the 3.2 to 2.7 Ma Grasberg Igneous Complex, porphyry ores of the 4.4 to 3.0 Ma Ertsberg Diorite 2.5 km to the south, and a series of skarns deposits.Together these deposits account for near 80 Mt of copper and around 3900 tonnes of gold (including inferred resources).
Mineralization: Mineralisation associated with the Ertsberg intrusive includes: The Ertsberg stockwork which contained a resource of 122 Mt @ 0.54% Cu, 0.90 g/t Au in 2005.The skarn mineralisation, which includes the: i). GB (Gunung Bijah) - 33 Mt @ 2.5% Cu, 0.8 g/t Au (the original reserve on which mining in the district was commenced), which is surrounded by Ertsberg Diorite near its NW margin; ii). GBT Complex (the vertically stacked GBT, IOZ & DOZ), 1.5 km east of GB on the northern contact, with reserves of >230 Mt @ 1% Cu, 0.8 g/t Au, iii). Dom Skarn, 0.5 km south of GBT, partially enclosed by the intrusive near its SE margin, with >70 Mt @ 1.4% Cu, 0.4 g/t Au, iv). Big Gossan within a fault zone cutting sediments to the west of the Ertsberg Diorite with 33 Mt @ 2.81% Cu, 1 g/t Au, v). Kucing Liar (dated at 3.42 Ma, the oldest mineralisation in the district, predating the Dalam Diorite) is associated with a fault zone between the two intrusive complexes, but close to the Grasberg complex, contains >225 Mt @ 1.42% Cu, 1.57 g/t Au.
|Block diagram showing the Grasberg Igneous Complex and zoned alteration. Weak stockwork and potassic alteration associated with South Kali Dikes are not shown.|
Haerwusu Coal Mine
The second biggest coal mine in the world by reserve, and China's largest open-cast coal mine
|Haerwusu Coal Mine|
Location: The Inner Mongolia Autonomous Region of China.
Owner: China’s state-run Shenhua Group.
Geological settings: The coal-bearing sequences in the Guanbanwusu Coal Mine include the Benxi Formation and the Taiyuan Formation (both Pennsylvanian) and the Shanxi Formation (Lower Permian) with a total thickness of 90–210 m (Fig. 2). Coal reserves of the Guanbanwusu Coal Mine amount to 92.04 Mt (Tehong, 2006).The Benxi Formation, with a thickness of 5.27–42 m, lies unconformably on thevMiddle Ordovician Majiagou Formation, and was deposited in a shallow marinevenvironment. The sediments are mainly composed of bauxite, sandstone, mudstone, and siltstone. The Taiyuan Formation, with a total thickness of 12–115 m, is mainly composed of gray and grayish-white quartzose sandstone, mudstone, siltstone, and coal, interbedded with dark-gray mudstone, siltstone, limestone, and thin-bedded quartzose sandstone. It was formed in paralic delta and tidal flat-barrier complex environments. The No. 6 Coal Seam is located at the uppermost Taiyuan Formation and has a thickness between 12.17 and 17.78 m (average 15 m). There are 9 partings with a cumulative thickness of 2 m in the No. 6 Coal Seam. The Shanxi Formation is composed of mainly of terrigenous coal-bearing clastic rocks dominated by sandstones. The formation has a thickness between 21 and 95 m, with an average of 52 m. It was formed in fluvial and delta deposite environments. The Shanxi Formation has five coal seams (Nos. 1, 2, 3, 4, and 5 Coal Seams), but only Nos. 3 and 5 are locally minable. The strata overlying the coal-bearing sequences are non-coal-bearing Upper Shihezi Formation, Lower Shihezi Formation and Shiqianfeng Formation.
|Stratigraphic column of the Guanbanwusu Mine, Jungar Coalfield.|
Al Sukari Gold Mine
Location: Marsa Alam, Red Sea, Egypt.
Geology of the Sukari gold mine area:
The mine occurs within a Late Neoproterozoic granitoid (Arslan 1989; Harraz 1991) that intruded older volcanosedimentary successions and an ophiolitic assemblage, both known as Wadi Ghadir me´lange (El Sharkawi and El Bayoumi 1979). The volcanosedimentary succession is composed of andesites, dacites, rhyodacites, tuffs and pyroclastics. Magmatic rocks are of calc-alkaline affinity (Akaad et al. 1995) and were formed in an island-arc setting (El Gaby et al. 1990). The dismembered ophiolitic succession is represented by a serpentinite at the base, followed upwards by a metagabbro-diorite complex and sheeted dykes. Metagabbro-diorite rocks and serpentinites form lenticular bodies (1–3 km2) as well as small bodies occur conformably scattered in the volcanosedimentary arc assemblage (Harraz 1991). All rocks are weakly metamorphosed (lower greenschist metamorphic facies), intensely sheared and transformed into various schists along shear zones. Mineralized quartz veins and talc-carbonate veinlets are common.
The fresh rock is
leucocratic, coarse-grained and pink in color. It has a heterogeneous
mineralogical composition and ranges from monzogranite to granodiorite with dominant
quartz, plagioclase and potash feldspars and less abundant biotite. The Sukari
granitoid has a trondhjemitic affinity (Arslan 1989) and belongs to the ‘‘Younger
Granite Suite’’ of Akaad and Nowier (1980).
argued for a transitional tectonic environment between within-plate,
volcanic-arc and syncollision granite fields. The age of the Sukari granitoid body
is poorly constrained (630–580 Ma, Harraz 1991) but documents Late Pan-African
magmatic activity in the area.
In the vicinity of
shear zones the granite is foliated, elsewhere, however, it has sharp intrusive
contacts against the older rocks. Along those shear zones serpentinite and
andesite is altered to listvenite rock (Khalaf and Oweiss 1993) that attains up
to 70 m in thickness and extends for several kilometers. At the intersection of
the two shear zones, where the gold mineralization is concentrated, the Sukari
granite is almost completely altered and transected by a large amount of quartz
Type of Deposit
The vein-type deposit is hosted in Late Neoproterozoic granite that
intruded island-arc and ophiolite rock assemblages. The vein-forming process is
related to overall late Pan-African shear and extension tectonics. At Sukari,
bulk NE– SW strike-slip deformation was accommodated by a local flower
structure and extensional faults with veins that formed initially at conditions
of about 300 C and 1.5–2 kbar. Gold is associated with sulfides in quartz veins
and in alteration zones. Pyrite and arsenopyrite dominate the sulfide ore
beside minor sphalerite, chalcopyrite and galena. Gold occurs in three distinct
positions: (1) anhedral grains (GI) at the contact between As-rich zones within
the arsenian pyrite; (2) randomly distributed anhedral grains (GII) and along
cracks in arsenian pyrite and arsenopyrite, and (3) large gold grains (GIII)
interstitial to fine-grained pyrite and arsenopyrite.
Fluid inclusion studies yield minimum veinformation temperatures
and pressures between 96 and 188 _C, 210 and 1,890 bar, respectively, which is
in the range of epi- to mesothermal hydrothermal ore deposits. The structural
evolution of the area suggests a longterm, cyclic process of repeated veining
and leaching followed by sealing, initiated by the intrusion of granodiorite.
This cyclic process explains the mineralogical features and is responsible for
the predicted gold reserves of the Sukari deposits. A characteristic feature of
the Sukari gold mineralization is the co-precipitation of gold and arsenic in
pyrite and arsenopyrite.
How the Gold is Extracted
Thousands of pounds of explosives, trucks and shovels as large as a house, and massive grinding
machines that can reduce hard rocks to dust are involved in the extraction process. In this way, Gold is extracted from one of the largest
open-air mines on the planet. The raw material excavated from the terraces in
the mine contains gold and arsenic in pyrite and arsenopyrite is a distinct
feature of the gold mineralisation at Sukari.
The fresh rock is leucocratic, coarse-grained and pink in color. It has a heterogeneous mineralogical composition and ranges from monzogranite to granodiorite with dominant quartz, plagioclase and potash feldspars and less abundant biotite. The Sukari granitoid has a trondhjemitic affinity (Arslan 1989) and belongs to the ‘‘Younger Granite Suite’’ of Akaad and Nowier (1980).
Harraz (1991) argued for a transitional tectonic environment between within-plate, volcanic-arc and syncollision granite fields. The age of the Sukari granitoid body is poorly constrained (630–580 Ma, Harraz 1991) but documents Late Pan-African magmatic activity in the area.
In the vicinity of shear zones the granite is foliated, elsewhere, however, it has sharp intrusive contacts against the older rocks. Along those shear zones serpentinite and andesite is altered to listvenite rock (Khalaf and Oweiss 1993) that attains up to 70 m in thickness and extends for several kilometers. At the intersection of the two shear zones, where the gold mineralization is concentrated, the Sukari granite is almost completely altered and transected by a large amount of quartz veins.
Type of Deposit & Mineralization
The vein-type deposit is hosted in Late Neoproterozoic granite that intruded island-arc and ophiolite rock assemblages. The vein-forming process is related to overall late Pan-African shear and extension tectonics. At Sukari, bulk NE– SW strike-slip deformation was accommodated by a local flower structure and extensional faults with veins that formed initially at conditions of about 300 C and 1.5–2 kbar. Gold is associated with sulfides in quartz veins and in alteration zones. Pyrite and arsenopyrite dominate the sulfide ore beside minor sphalerite, chalcopyrite and galena. Gold occurs in three distinct positions: (1) anhedral grains (GI) at the contact between As-rich zones within the arsenian pyrite; (2) randomly distributed anhedral grains (GII) and along cracks in arsenian pyrite and arsenopyrite, and (3) large gold grains (GIII) interstitial to fine-grained pyrite and arsenopyrite.
Fluid inclusion studies yield minimum veinformation temperatures and pressures between 96 and 188 _C, 210 and 1,890 bar, respectively, which is in the range of epi- to mesothermal hydrothermal ore deposits. The structural evolution of the area suggests a longterm, cyclic process of repeated veining and leaching followed by sealing, initiated by the intrusion of granodiorite. This cyclic process explains the mineralogical features and is responsible for the predicted gold reserves of the Sukari deposits. A characteristic feature of the Sukari gold mineralization is the co-precipitation of gold and arsenic in pyrite and arsenopyrite.
Kidd Creek Mine It is the world's deepest copper/zinc mine.
Location: Timmins, Ontario, Canada.
Products: Copper & Zinc.
Owner: Xstrata Copper.
Deposit Type: The Kidd deposit is one of the largest volcanogenic massive sulfide ore deposits in the world, and one of the world's largest base metal deposits.
Ore Geology: Kidd Creek is based on a rich, steeply dipping volcanogenic sulphide deposit located in the Archaean Abitibi greenstone belt. There are two major orebodies, with associated smaller lenses. The ore is hosted in felsic rocks of the Kidd Volcanic Complex and is cut by mafic sills and dykes. Structural deformation resulting from several phases of folding and faulting affects the distribution of sulphide lenses.
Three ore types predominate: massive, banded and bedded (MBB) ores (pyrite, sphalerite, chalcopyrite, galena and pyrrhotite); breccia ores containing fragments of the MBB ores; and stringer ores consisting of irregular chalcopyrite stringers cutting a siliceous volcaniclastic host.
Geological setting & Stratigraphic section of the mine:
The Kidd Creek Volcanic Complex is interpreted to have formed within a proto-arc geodynamic setting, with the high silica FIII rhyolites a product of crustal extension during rifting and melting of the lithosphere (Wyman et al., 1999; Prior et al., 1999). A graben interpreted to contain the Kidd VMS deposit is consistent with this geodynamic setting and a recent volcanic reconstruction of the North Rhyolite by DeWolfe et al. (2003), suggest a minimum graben width of 5 to 7 km (Gibson and Kerr, 1993; Bleeker, 1999). Fissures that controlled the eruption and emplacement of the Footwall and QP rhyolites may be graben-parallel structures (Prior, 1996).
The simplified stratigraphic column in Figure 3 provides a general overview of the Kidd Mine stratigraphy and location of massive sulfide deposits. Komatiitic flows and intrusions constitute the base of the known stratigraphic sequence and likely formed a broad, low-relief lava plain upon which the Kidd Creek rhyolitic dome and ridge complex was constructed. The minimum thickness of the komatiitic unit is estimated at 500 metres.
Figure 2. Kidd Mine ore-bodies looking east from surface to 10,200 ft
Mining operation and reserves :
The mine started production in 1966 from an open pit. The orebody is now mined at depth through three shafts as the No.1, No.2 and No.3 Mines. Phase 2 of No.3 Mine is currently being developed. Mine D will extend Kidd Creek below No 3, from a depth of 2,100m to 3,100m.
Blasthole stoping with cemented backfill is used to extract the ore underground, Kidd Creek being the world’s second-largest user of cemented backfill (after Mt Isa in Australia). Blastholes are drilled using Ingersoll Rand, Mission and Cubex drills and broken ore is hauled underground by Tamrock load-haul-dump units. The hoisting shafts are equipped with an ABB Hoist Automation System, which has significantly increased the efficiency of raising ore from depth.
At the end of 2005, Kidd Creek’s proven and probable reserves were stated as being 19Mt grading 1.8% copper, 5.5% zinc, 0.18% lead and 53g/t silver. Measured and indicated resources totalled 2.6Mt at 2.2% copper, 6.3% zinc, 0.2% lead and 48 g/t silver, with a further 11.9Mt in inferred resources at 2.7% copper, 4.8% zinc, 0.3% lead and 81g/t silver.
Barrie, C.T., 1999. Komatiitic flows of the Kidd Creek footwall,
Abitibi Subprovince, Canada: In Hannington, M.D., and
Barrie, C.T., eds. The Giant Kidd Creek Volcanogenic Massive
Sulfide Deposit, Western Abitibi Subprovince, Canada. Economic
Geology, Monograph 10, p. 143-162.
Beaty, D.W., Taylor, H.P., & Coad, P.R., 1988. An oxygen
isotope study of the Kidd Creek, Ontario, volcanogenic massive
sulfide deposit: Evidence for high heat 18O ore fluid. Economic
Geology, v. 83, p. 1-18.
Bleeker, W., 1999. Structure, stratigraphy, and primary setting
of the late Archean Kidd Creek Volcanogenic massive sulfide
deposit: A semi-quantitative reconstruction: In Hannington,
M.D., and Barrie, C.T., eds.
The Diavik Diamond Mine
|Diavik Diamond Mine|
Location: Lac de Gras, Northwest Territories, Canada.Products: Diamonds.
Owner: Dominion Diamond Corporation and Diavik Diamond Mines Inc.
Ore Type: The mine consists of three kimberlite pipes.
Geological notes of Diamond and The Diavik Mine:
Our knowledge of the primary sources of diamonds in the lithospheric upper mantle is mainly derived from the studies of mantle xenoliths in kimberlites and of mineral inclusions in diamonds themselves. Inclusions in diamonds preserve evidence of the physical and chemical environment at the time of diamond formation, presumed to have occurred early in Earth’s history (e.g. Richardson et al. 1984). Mantle xenoliths, in contrast, integrate a more protracted history that may have involved multiple stages of melt extraction, and thermal re-equilibration in response to short lived thermal pulses or secular cooling, and metasomatic re-enrichment. Rare diamond-bearing peridotite xenoliths provide unique opportunities to study the principal source of diamonds in the Earth’s mantle directly and to obtain information on the evolution of cratonic lithosphere, spanning the time from diamond formation to kimberlite eruption. Based on inclusion studies, peridotitic diamonds largely formed in depleted harzburgitic sources (Gurney and Switzer 1973; Gurney 1984). Evidence for changes in the composition of peridotitic subcratonic lithospheric mantle over time, involving a decreasing ratio of harzburgite to lherzolite (Griffin et al. 2003), raises the possibility that diamonds are stored in mantle rocks that are compositionally quite distinct from the environment of diamond formation. This would have important implications for diamond exploration, because indicator mineral assessment, evaluating the state of mantle lithosphere at the time of kimberlite eruption, is strongly based on chemical criteria derived from inclusion studies depicting the environment of diamond formation. One of the key questions for our study of diamondiferous peridotite xenoliths from Diavik, therefore, is verifying the extent to which the originally highly depleted signature at the time of diamond formation has been preserved or modified during subsequent metasomatic events.
Based on the composition of xenoliths and garnet xenocrysts, Griffin et al. (1999a) inferred that the mantle beneath the Lac de Gras area is chemically and thermally stratified. They suggested that an ‘‘ultradepleted’’, predominantly harzburgitic layer overlies a less depleted, predominantly lherzolitic layer with the transition being located at *145 km depth. Griffin et al. (1999a) proposed the shallower ‘‘ultradepleted’’ layer to represent Mesoarchean oceanic or sub-arc mantle lithosphere and the lower layer to be the frozen head of a Neoarchean plume derived from the lower mantle. Aulbach et al. (2007) suggested that the deeper portions of the lower layer experienced secondary re-enrichment in FeO (Aulbach et al. 2007). An alternative model for the formation of subcratonic lithospheric mantle involves stacking of highly depleted Archean oceanic lithospheric mantle beneath early continents (e.g. Schulze 1986; Helmstaedt and Schulze 1989; Bulatov et al. 1991; de Wit 1998; Stachel et al. 1998). In this model, the observed increase in fertility with depth in the central Slave craton may relate to metasomatism by infiltrating fluids/melts ascending from the asthenosphere (Stachel et al. 2003).
Aulbach S, Griffin WL, Pearson NJ, O’Reilly SY, Doyle BJ (2007)
Lithosphere formation in the central Slave Craton (Canada):
plume subcretion or lithosphere accretion. Contrib Mineral
Bernstein S, Kelemen PB, Hanghøj K (2007) Consistent olivine Mg#
in cratonic mantle reflects Archean mantle melting to the
exhaustion of orthopyroxene. Geology 35:459–462
Bleeker W, Davis WJ (1999) The 1991–1996 NATMAP Slave
province project: introduction. Can J Earth Sci 36:1033–1042
Boyd SR, Kiflawi I, Woods GS (1994) The relationship between
infrared absorption and the A defect concentration in diamond.
Philos Mag B 69:1149–1153
Boyd SR, Kiflawi I, Woods GS (1995) Infrared absorption by the B
nitrogen aggregate in diamond. Philos Mag B 72:351–361
Griffin WL, Cousens DR, Ryan CG, Sie SH, Suter GF (1998) Ni in
chrome pyrope garnets: a new geothermometer. Contrib Mineral
Bingham Canyon (Kennecott) Copper Mine
It is the world's deepest man-made open pit excavation.
|Bingham Canyon (Kennecott) Copper Mine|
Location: Salt Lake County, Utah, United States.
Owner: Rio Tinto Group.
Ore Type : Porphyry copper deposit.
The history of the Mine:
Bingham Canyon was settled in 1848 by the Bingham brothers, Thomas and Sanford, who were ranchers with no mining experience. In 1863, soldiers stationed at Fort Douglas in Salt Lake City explored the canyon and discovered lead ore. Utah’s first mining district was created in the Bingham Canyon area that same year. In 1893, Daniel Jackling, a metallurgical engineer, and Robert Gemmell, a mining engineer, studied the deposit and recommended developing the ore body through a revolutionary open-pit mining method and processing the ore on a large, industrial scale. The miners and their families lived near Bingham Canyon in places called Highland Boy, Copper Heights, Copperfield, Carr Fork, Heaston Heights, Telegraph, Dinkeyville, Terrace Heights, Greek Camp and Frog Town. At one point, the population in the area approached 20,000 people. In 1903, the Utah Copper Company was formed to develop the mine, based on the recommendations of Mr. Jackling and Mr. Gemmell. In 1906, the first steam shovels began mining away the waste rock that covered the ore body. The ore was found in a part of the mountain that divided the main canyon.
Geology of the Mine:
Every deposit of ore in the world is unique. There are no two ore bodies that are alike. Geologic forces were at work in the Oquirrh Mountains between 260 and 320 million years ago (Late Paleozoic Period). About 30 to 40 million years ago, molten, metal-bearing rock deep within the earth’s crust began to push toward the surface and formed Bingham’s ore deposit. Volcanoes erupted above the evolving ore body. This particular ore body contains primarily copper, gold, silver and molybdenum.
Tiny grains of ore minerals, mostly copper and iron sulfides, are scattered within what is called “host rock.” Because there is far more host rock than there are minerals, it is known as a low-grade ore deposit. Because this is a low-grade deposit, a ton of ore contains only about 10.6 pounds of copper. For every ton of ore removed, about two tons of overburden must first be removed to gain access to the ore.
How big is the Bingham Canyon Mine?
Kennecott Utah Copper’s (KUC) Bingham Canyon Mine has produced more copper than any mine in history— about 18.1 million tons.
The mine is 2¾ miles across at the top and ¾ of a mile deep. You could stack two Sears Towers (now known as the Willis building), on top of each other and still not reach the top of the mine. The mine is so big it can be seen by space shuttle astronauts as they pass over the United States. By 2015, the mine will be more than 500 feet deeper than it is now. If you stretched out all the roads in the open-pit mine— some 500 miles of roadway — you’d have enough distance to reach from Salt Lake City to Denver. KUC mines about 55,000,000 tons of copper ore and 120,000,000 tons of overburden per year.
The mining process:
Bingham Canyon Mine This is where the mining process begins. Every day, Kennecott Utah Copper mines about 150,000 tons of copper ore and 330,000 tons of overburden. The ore containing copper, gold, silver and molybdenum is hauled and deposited in the in-pit crusher and sent to the Copperton Concentrator.
Copperton Concentrator From the mine, ore is transported on a five-mile conveyor and stockpiled at the Copperton Concentrator. There the ore is ground into fine particles. The smaller pieces are then combined with air, water and chemical reagents to separate the valuable minerals from the waste rock. The mineral bearing concentrate is then transported to the smelter through a pipeline.
Tailings: Are the leftover rock material that have had most of the valuable metals removed. Tailings are sent through a pipeline from the Copperton Concentrator to the tailings impoundment north of the town of Magna where they are stored.
Smelter: At the smelter, the copper concentrate is transformed into liquid copper through a flash smelting process. The copper matte is processed in the furnace to produce 98.6 percent blister copper. From there, the 720 pound copper plates, called anodes, are sent to the refinery.
Refinery: At the refinery, anodes are lowered into electrolytic cells containing a stainless steel blank and acidic solution. For 10 days, an electric current is sent between the anode and the cathode, causing the copper ions to migrate to the steel sheet. The other impurities, including gold and silver, fall into the bottom of the cell and are recovered in the Precious Metals plant. This process forms a plate of 99.99% pure copper. The copper is separated from the steel sheet and sent to market.
Golden Sunlight Mine
Location: Jefferson County, Montana, United States.
Owner: Barrick Gold Corporation.
Ore Type: Breccia pipe.
Reserves: Golden Sunlight produced 86,000 ounces of gold in 2014 at all in sustaining costs of $1,181 per ounce1. Proven and probable mineral reserves as at December 31, 2014, were 127,000 ounces of gold2.
In 2015, gold production is expected to be 90,000-105,000 ounces at all-in sustaining costs of $1,000-$1,025 per ounce.
Geological setting & Mineralization
The Golden Sunlight gold-silver deposit is hosted by a breccia pipe that cuts sedimentary rocks of the Middle Proterozoic Belt Supergroup and sills of a Late Cretaceous rhyolite porphyry (Porter and Ripley, 1985; Foster, 1991a, 1991b). At depth, rhyolite porphyry forms the matrix for fragments of the pipe. Creation of the pipe appears to be related to emplacement of an underlying hypabyssal stock related to the sills. Crosscutting the breccia pipe are hydrothermally altered lamprophyre dikes that postdate the gold-silver ore; locally, these dikes may have created areas of high-grade ore in the breccia pipe near their margins. The timing of emplacement of various igneous rocks and the hydrothermal alteration related to mineralization at the deposit.
Gold and silver in the region was concentrated along northeast-striking, high-angle faults and shear zones, some of which cut the breccia pipe and along which lamprophyre dikes have been emplaced (Porter and Ripley, 1985). These structures are thought to be part of a regional, northeast-striking zone of crustal weakness that has been intermittently active from the Proterozoic to the present (Foster and Chadwick, 1990; Foster 1991a). Because some hydrothermally altered and mineralized lamprophyre dikes are preferentially emplaced along structures that cross-cut the breccia pipe, their relationship to mineralization of the breccia pipe has been ambiguous. Certainly their emplacement is later than that of the pipe, and the simplest interpretation is that lamprophyre emplacement postdates mineralization. But, because the northeast-striking shear zones, veins, and dikes contain high-grade ore in places, a mineralizing process was obviously continuing during emplacement of the lamprophyre bodies.
Since its beginnings in 1982, Golden Sunlight Mine has continued to add resources to extend the life of the mine. Currently, the Montana DEQ is conducting the environmental review necessary to grant permission for mining additional resources referred to as the North Area Pit and South Area Layback, which would extend the mine life into 2016. Additional exploration is ongoing north of the Mineral Hill pit site with drilling activity in the Bonnie/Microwave area. 2013 will bring its own mix of success and challenge, so it is important that we remain intently focused on continuous improvement. As we work to deliver safe and profitable gold production, we cannot lose sight of our long-range goals—community partnership, environmental stewardship and most importantly, the safety and health of our people. I thank everyone again for the warm reception and look forward to getting to know you better in the coming months.
Safety and Health
We made great strides in improving our safety record, an achievement we celebrated in March, when we received Barrick’s Excellence Award for Best Safety Performance. As of first quarter 2013, GSM has gone five and a half years, and 2.7 million employee hours, without a lost-time incident, and over a year without a medical aid treatment incident. We still have more work to do in order to achieve our goal of zero incidents. As with most things, safety starts and ends with leadership. I expect all of our employees to be leaders when it comes to ensuring safety and continuing to send all GSM employees and contractors home safe and healthy every day.
Golden Sunlight Mine was the recipient of the prestigious Bureau of Land Management (BLM) 2012 Mineral Environmental Award for our third-party ore processing and reclamation initiatives. Golden Sunlight Mine initiated the program to assist small miners to mill outside “ores” and to assist with legacy mine materials containing reasonable concentrations of precious metals. In presenting the award, the BLM stated: “The Golden Sunlight Mine has turned liabilities into environmental and economic benefit—greatly enhancing the quality of the environment, saving taxpayer dollars, and creating local jobs.”
Lac des Iles Mine
|Lac des Iles Palladium Mine|
Location: Toronto, Canada.
Products: PGE Deposits.
By product: Gold. Platinum, silver, nickel, and copper.
Owner: North American Palladium Ltd.
GEOLOGICAL SETTING AND MINERALIZATION
The Property is underlain by mafic to ultramafic rocks of the Lac des Iles Intrusive Complex in the Wabigoon Subprovince of the Canadian Shield. The LDI-IC is an irregularly-shaped Neoarchean-age mafic-ultramafic intrusive body having maximum dimensions of approximately 9 km in the north-south direction and approximately 4 km in the east-west direction. The complex incorporates three discrete intrusive bodies viz.:
The North Lac des Iles Intrusion (NLDI) characterized by a series of relatively flatlying and nested ultramafic bodies with subordinate mafic rocks.
The Mine Block Intrusion (MBI), host to all of the stated Lac des Iles mineral reserves and resources (refer to Sections 14.0 and 15.0).
The South Lac des Iles Intrusion (SLDI), a predominantly mafic (gabbroic) intrusion having many similarities to the MBI in terms of rock types and textures. To date, NAP’s exploration activities have been focused on the MBI. The MBI is a small, teardrop-shaped mafic complex with maximum dimensions of 3 km by 1.5 km and having an elongation in an east-northeast direction. The MBI consists of gabbroic (noritic) rocks having highly-variable plagioclase: pyroxene proportions, textures, and structures. The MBI was emplaced into predominantly intermediate composition orthogneiss basement rocks. The MBI is intersected by a series of brittle to ductile faults and shear zones, some of which appear to control the distribution of higher-grade palladium mineralization. A major north-trending shear zone appears to have cut the western end of the MBI and is spatially associated with the development of high-grade palladium mineralization. Textural and mineralogical variability is greatest in the outer margins of the MBI, especially along the well documented western and northern margins that host most of the known palladium resources. Commonly observed textures in the noritic marginal units of the MBI include equigranular, fine- to coarse-grained (seriate textured), porphyritic, pegmatitic, and varitextured. Platinum-group element and copper-nickel sulphide mineralization in the MBI is found in a variety of structural and geological settings but in general is characterized by the presence of small amounts (e.g., typically less than 2%) of fine- to medium-grained disseminated iron-copper-nickel sulphides within broadly stratabound zones of platinum group elements (PGE) and gold enrichment.
The mineralization is commonly associated with varitextured gabbroic rocks; coarse-grained noritic rocks; and local, intensive zones of amphibolitization, chloritization and shearing. An important, distinguishing characteristic of the MBI mineralization relative to other PGE deposits is the consistently high palladium:platinum ratio, commonly averaging 10:1 or higher. Sulphide mineral assemblages are dominated by pyrite with lesser pyrrhotite, chalcopyrite, pentlandite, and millerite.
MINERAL RESERVE ESTIMATE
The mineral reserves were estimated by applying wireframe models depicting stope and pillar shapes to the underground geological block models provided by NAP. NAP aslo provided a separate, more historical geological block model for open pit evaluations, as well as RGO stockpile resource information that was used to estimate the amount of the stockpiled resource material that would be recovered during the LOM time period and accordingly be brought into the reserves. For the underground models, a mineral resource envelope was established with a 1.0 g/t palladium resource grade and a block size of 5 m by 5 m by 5 m. For the open pit block model, NAP used a 2003 block model that had a block size for pit evaluations of 15 m by 15 m by 8 m. Tetra Tech’s senior geologist reviewed and validated each of NAPs submitted block models, prior to use.
|Mineral Reserves at the Cut‐off Grades|
Barrick Goldstrike Mine
It is owned and operated by the world's largest gold mining company, & it is the largest gold mine in North America.
|The Goldstrike mine|
Location: Eureka County, Nevada, United States.
Products: Gold , Silver.
Ore Type: Epithermal gold deposite in carbonate or silicate sedimentary rocks.
Owner: Barrick Gold.
Ounces of gold produced in 2014 >> 902,000
Ounces of proven and probable gold reserves >> 9,614,000
Overview: The Goldstrike mine, one of the top five gold-producing mines in the world, is Barrick Gold’s largest producing mine. The mine consists of both the Betze-Post open-pit and the Meikle and Rodeo underground mines (the “Goldstrike Mine”). Barrick, which is also the biggest gold producer in the world, has operated the mine for over 20 years (since 1987). The mine is located on the Carlin Trend in north-central Nevada, USA, about 40 kilometers northwest of the city of Elko. In 2007, the Goldstrike operation produced 1.63 million ounces of gold at average total cash costs of $373 per ounce. The Goldstrike property comprises approximately 4,197 hectares of surface rights ownership and approximately 3,535 hectares of mineral rights ownership on the Carlin Trend, a prolific gold producing region of North America. The northwestsoutheast trend is an 80 km long, 8 km wide belt that contains more than 20 major gold deposits. The operation employs approximately 1,600 employees.
Geological settings & Mineralization : The Goldstrike mine complex (including the Betze-Post-Screamer and Meikle Rodeo deposits).
Betze-Post Open Pit
After Barrick took over the operation, two sulphide ore zones were identified as the Betze and Deep Post deposits in 1987. Since it entered production in 1993, the Betze-Post pit has been a truck-and-shovel operation using large electric shovels. The Betze-Post ore zones extend for 1,829 meters northwest and average 183 to 244 meters in width and 122 to 183 meters in thickness. The Post oxide orebody occurs in the siliceous siltstones, mudstones, argillites and minor limestones of the Rodeo Creek Formation. The Betze and Post oxide deposits are hosted in sedimentary rocks of Silurian to Devonian age. The mineralization of the Betze-Post pit was captured by structural traps developed by Mesozoic folding and thrust faults. Volcanic and sedimentary rocks filled ranges and basins formed by Tertiary faulting. The Tertiary volcanism initialized gold mineralization approximately 39 million years ago.
In 2007, the open pit mine produced 1,215,000 ounces of gold from 136.9 million tons mined and 10.5 million tons processed. The average grade processed is 0.136 oz/ton with a recovery rate of 85.5%. The average total cash cost was $355 per ounce. The open pit mine has proven and probable reserves totaling 12.19 million ounces from 94.9 million tons grading 0.128 oz/ton. The mine is expected to sustain the current production level for approximately 8 years, based on existing reserves. Most of the open pit mine is subject to a net smelter return of up to 4% and a net profits interest of up to 6%.
Meikle Rodeo deposits
The Meikle deposit occurs in hydrothermal and solution collapse breccias in the Bootstrap Limestone of the Roberts Mountains Formation. The gold at Goldstrike was carried into the various orebodies by hot hydrothermal fluids, and deposited with very fine pyrite and silica. Over time, the pyrite oxidized, freeing the gold and making its extraction relatively easy, as in the Post Oxide deposit. In the deeper deposits – Betze, Rodeo and Meikle – the gold is still locked up with the iron sulphide and an additional processing step (autoclaving or roasting) is required to free the gold. Two haulage drifts connect the Meikle and Rodeo orebodies.
The drifts are accessed from two shafts and by a decline at the bottom of the open pit mine. In the year ended December 31, 2007, the underground mine produced 413,186 ounces of gold at an average total cash cost of $431 per ounce. Proven and probable reserves underground are estimated at 7.42 million tons at 0.364 oz/ton, containing 2.7 million ounces. The Goldstrike’s total (open pit and underground) proven and probable mineral reserves as of December 31, 2007 are estimated at 14.9 million ounces of gold. The underground mine, which originally produced at a rate of approximately 2,000 tons of ore per day, averaged 3,562 tons per day in 2007. Based on current reserves and production capacity, the expected mine life is 9 years. The maximum royalties payable on the Meikle deposit are a 4% net smelter return and a 5% net profits interest.
Mining Processing & operations: The Goldstrike complex consist of three distinct mines: the large Betze-Post open pit mine, and the Meikle and Rodeo underground mines. The ore from all three mines is milled and leached by the cyanide process. Carlin-type gold deposits host gold mainly as microscopically fine grains. Refractory non-carbonaceous sulphide ore is treated in an autoclave followed by a carbon-in-leach (CIL) cyanidation circuit. Carbonaceous ore, also refractory, is treated with a roaster followed by a CIL circuit. The two treatment facilities treat ores from both the open pit and underground mines. Recovered gold is processed into doré on-site and shipped to outside refineries for processing into gold bullion.
In 2008 the Betze-Post open-pit mine produced 1,281,450 oz (36,328 kg) of gold and 152,886 oz (4,334.2 kg) of silver, while the Meikle-Rodeo underground operations yielded 424,687 oz (12,039.7 kg) of gold and 51,438 oz (1,458.2 kg) of silver. This was 30% of the total 5,698,000 oz (161,500 kg) output of all gold mining operations in Nevada.
Non-carbonaceous sulphide (refractory) ore is treated at an autoclave and carbon-in-leach (CIL) cyanidization circuit. Carbonaceous ore is treated at the roaster and CIL circuit, since the active carbon content in carbonaceous ore responds poorly to autoclaving. The two facilities treat ores from both the open pit and underground mines and, when combined, have a design capacity of 33,000 to 35,000 tons per day. Recovered gold is processed into doré on-site and shipped to outside refineries for processing into gold bullion. A modified pressure leach technology was successfully tested last year and it will be used to process ores that would otherwise have been treated at the roaster facility, consequently extending the life of the autoclave. The property also has a 115 megawatt natural gas-fired power plant, providing a significant portion of the operation’s power requirements off-grid.
The Ranger Uranium Mine
|The Ranger Uranium Mine|
Location: Kakadu National Park, Northern Territory, Australia.
Owner: Energy Resources of Australia Limited.
Deposit Type: Unconformity-related uranium deposits.
Overview: In 1969 the Ranger orebody was discovered by a Joint Venture of Peko Wallsend Operations Ltd (Peko) and The Electrolytic Zinc Company of Australia Limited (EZ). In 1974 an agreement set up a joint venture consisting of Peko, EZ and the Australian Atomic Energy Commission (AAEC).
In 1978, following a wide ranging public inquiry (the Ranger Uranium Environmental Inquiry) and publication of its two reports (the Fox reports), agreement to mine was reached between the Commonwealth Government and the Northern Land Council, acting on behalf of the traditional Aboriginal land owners. The terms of the joint venture were then finalised and Ranger Uranium Mines Pty Ltd was appointed as manager of the project.
In August 1979 the Commonwealth Government announced its intention to sell its interest in the Ranger project. As a result of this, Energy Resources of Australia Ltd (ERA) was set up with 25% equity holding by overseas customers. In establishing the company in 1980 the AAEC interest was bought out for $125 million (plus project costs) and Peko and EZ became the major shareholders. Several customers held 25% of the equity in non-tradable shares. Ranger Uranium Mines Pty Ltd became a subsidiary of ERA. During 1987-8 EZ's interest in ERA was taken over by North Broken Hill Holdings Ltd and that company merged with Peko. Consequently ERA became a 68% subsidiary of North Limited, and this holding was taken over by Rio Tinto Ltd in 2000. In 1998 Cameco took over Uranerz, eventually giving it 6.69% of ERA, and Cogema took over other customer shares, giving it (now Areva) 7.76%.
Late in 2005 there was a rearrangement of ERA shares which meant that Cameco, Cogema and a holding company (JAURD) representing Japanese utilities lost their special unlisted status and their shares became tradable. The three companies then sold their shares, raising the level of public shareholding to 31.61%.
Features associated with some of the unconformity-related uranium deposits in the Alligator Rivers, Rum Jungle and South Alligator Valley uranium fields are as follows (modified after Ewers & others, 1984; Mernagh, Wyborn & Jagodzinski, 1998): The host rocks occur in intracontinental or continental margin basins; the deposits are near to a late Palaeoproterozoic oxidised thick cover sequence (>1 km) of quartz-rich sandstone;
The basement is chemically reduced, containing carbonaceous/ferrous iron-rich units or feldspar-bearing rocks;
The deposits are associated with a Palaeoproterozoic/late Palaeoproterozoic unconformity and with dilatant brecciated fault structures, which cut both the cover and basement sequences and separate reduced lithologies from the oxidised cover sequence;
Most of the large deposits in the Alligator Rivers and the Rum Jungle fields are in stratabound ore zones and have a regional association with carbonate rock/pelitic rock contact, but an antipathetic relationship with carbonate in the ore zones;
The major Australian deposits lie close to an unconformity although the Jabiluka deposit is still open some 550 m below the unconformity;
The known major uranium deposits are present where the oxidised cover sequence is in direct contact with the reducing environments in the underlying pre-1870 Ma Archaean–Palaeoproterozoic basement and not separated by an intervening sequence, as by the El Sherana and Edith River Groups in the South Alligator Valley uranium field.
|Local stratigraphy of The Ranger Mine|
Alteration features associated with the deposits are:
Alteration extends over 1 km from the deposits,
Alteration is characterised by sericite–chlorite ± kaolinite ± hematite,
Mg metasomatism and the formation of late-stage Mg rich chlorite are common,
Strong desilicification occurs at the unconformity.
Source of Uranium mineralization
Archaean and Palaeoproterozoic granites of the Alligator Rivers and South Alligator Valley uranium fields have uranium contents which are well above the crustal average of 2.8 ppm U (Wyborn, 1990a). Granites and granitic gneisses of the Nanambu complex contain 3–50 ppm U; tonalites, granitic gneisses and granitic migmatites of the Nimbuwah complex have 1–10 ppm U. The Nabarlek Granite that has been intersected in drill holes below the Nabarlek deposit has 3–30 ppm U, and the Tin Camp and Jim Jim Granites also have high uranium contents. The Malone Creek Granite (South Alligator Valley) has 11–28 ppm U. Wyborn (1990b) suggested that the underlying crust in the region of these uranium fields is enriched in uranium. Maas (1989) concluded from Nd–Sr isotopic studies that for Jabiluka, Nabarlek and Koongarra, the uranium was derived from two sources: the Palaeoproterozoic metasediments and a post-unconformity source, probably highly altered volcanics within the Kombolgie Subgroup. Maas (1989) also proposed that these orebodies formed when hot oxidising meteoric waters, which contained uranium derived from volcano-sedimentary units within the Kombolgie, reacted with reducing metasediments of the Palaeoproterozoic basement.
Processing: Following crushing, the ore is ground and processed through a sulfuric acid leach to recover the uranium. The pregnant liquor is then separated from the barren tailings and in the solvent extraction plant the uranium is removed using kerosene with an amine as a solvent. The solvent is then stripped, using an ammonium sulphate solution and injected gaseous ammonia. Yellow ammonium diuranate is then precipitated from the loaded strip solution by raising the pH (increasing the alkalinity), and removed by centrifuge. In a furnace the diuranate is converted to uranium oxide product (U3O8).
Reserves & Resources: The Ranger 1 orebody, which was mined out in December 1995, started off with 17 million tonnes of ore some of which is still stockpiled. The Ranger 3 nearby is slightly larger, and open pit mining of it took place over 1997 to 2012.
In 1991 ERA bought from Pancontinental Mining Ltd the richer Jabiluka orebody (briefly known as North Ranger), 20 km to the north of the processing plant and with a lease adjoining the Ranger lease. ERA was proposing initially to produce 1000 t/yr from Jabiluka concurrently with Ranger 3. The preferred option involved trucking the Jabiluka ore to the existing Ranger mill, rather than setting up a new plant, tailings and waste water system to treat it on site as envisaged in an original EIS approved in 1979. However, all these plans are now superseded – see Australia's Uranium Deposits and Prospective Mines paper.
In the Ranger 3 Pit and Deeps the upper mine sequence consists of quartz-chlorite schists and the lower mine sequence is similar but with variable carbonate (dolomite, magnesite and calcite). The primary ore minerals have a fairly uniform uranium mineralogy with around 60% coffinite, 35% uraninite and 5% brannerite. In weathered and lateritic ores the dominant uranium mineralogy is the secondary mineral saleeite with lesser sklodowskite.
In the second half of 2008 a $44 million processing plant was commissioned to treat 1.6 million tonnes of stockpiled lateritic ore with too high a clay content to be used without this pre-treatment. Following initial treatment the treated ore is fed into the main plant, contributing 400 t/yr U3O8 production for seven years. A new $19 million radiometric ore sorter was commissioned at the same time, to upgrade low-grade ore and bring it to sufficient head grade to go through the mill. It will add about 1100 tonnes U3O8 to production over the life of the mine, and be essential for beneficiating carbonate ore from the lower mines sequence of the Ranger 3 Deeps.
A feasibility study into a major heap leach operation for 10 Mt/yr of low-grade ore showed the prospect of recovering up to 20,000 t U3O8 in total. Column leach trials were encouraging, yielding extractions of greater than 70% at low rates of acid consumption. The facility would consist of fully lined heaps of material about 5m high and covering about 60-70 ha. These will be built and removed on a regular cycle and the residues stored appropriately after leaching is completed. The acid leach solutions would be treated in a process similar to that used in the existing Ranger plant and recycled after the uranium is removed from the pregnant liquor. ERA applied for government (including environmental) approval for the project, which was expected to begin operation in 2014, but in August 2011 ERA announced that the plan was shelved due to high capital costs and uncertain stakeholder support. As a result, ore reserves of 7,100 tonnes of uranium oxide were reclassified as resources.
In 2006 the projected operating life of the Ranger plant was extended to 2020 due to an improvement in the market price enabling treatment of lower grade ores, and in 2007 a decision to extend the operating Ranger 3 open pit at a cost of $57 million meant that mining there continued to 2012. However, reassessment of the low-grade stockpile in 2011 resulted in downgrading reserves by 6100 t U3O8. The #3 pit is now being backfilled, and to mid-2014, 31 million tonnes of waste material had been moved there. It will then be used as a tailings dam.
Boddington Gold Mine
|Boddington Gold Mine|
Location: Boddington ,Western Australia.
Ore Type: Lode Deposits.
Products: Gold. Secondary Copper.
Owner: Newmont Mining.
Reserves: By the end of 2011, proven ore reserves at Boddington were 20.3 million ounce (moz) of gold and 2.26 billion pounds (blbs) of copper.
Overview: Boddington Gold Mine (BGM) is located about 130km south-east of Perth in Western Australia. The largest gold mine in the country, it is poised to become the highest producing mine once production ramps up over the next few years. The $2.4bn project was initially a three-way joint venture between Newmont Mining, AngloGold Ashanti and Newcrest Mining. In 2006 Newmont bought Newcrest's 22.22% share, bringing its interest to 66.67% and ending any Australian ownership. AngloGold owned the remaining 33.33%. In June 2009, Newmont became the sole owner of the mine by acquiring the 33.3% interest of AngloGold. The original, mainly oxide open-pit mine was closed at the end of 2001.
The project has an attributable capital budget of between A$0.8bn and A$0.9bn. On 23 July 2009, the project, including the construction of the treatment plant, was completed. Production began in the third quarter of 2009. The first gold and copper concentrate was produced in August 2009.
Approximately 100,000t of ore was processed by mid-August. Gold production began on 30 September 2009. By 19 November 2009, the mine achieved commercial production. The mine was officially inaugurated in February 2010. The project had an attributable capital budget of between A$0.8bn and A$0.9bn. It employs 900 workers.
Based on the current plan, mine life is estimated to be more than 20 years, with attributable life-of-mine gold production expected to be greater than 5.7Moz.
In May 2012, Newmont decided to seek the expansion of mine life to 2052 by combining the north and south Wandoo open pits. It also plans to expand the waste rock facility to two billion metric tons.
Newmont and Anglo had focused their exploration activities on the poorly explored areas of the greenstone belt outside the already identified Boddington Expansion resource. The exploration strategy was to identify the resource potential of the remainder of the greenstone belt, with the emphasis on high-grade lode-type deposits.
Geological settings & Mineralization:
The Boddington gold mine is hosted in Archean volcanic, volcaniclastic, and shallow-level intrusive rocks that form the northern part of the Saddleback greenstone belt, a fault-bounded sliver of greenstones located in the southwestern corner of the Yilgarn craton, Western Australia. Total Au content of the Boddington gold mine (past production plus in situ resource) exceeds 400 metric tons, making the Boddington gold mine one of the largest Au mines currently operating in Australia.Geologic mapping and radiometric dating indicate that five phases of igneous activity occurred during development of the Saddleback greenstone belt. Basaltic, intermediate, and minor felsic volcanism occurred between approximately 2714 and 2696 Ma and again at approximately 2675 Ma. An older suite of ultramafic dikes was emplaced between approximately 2696 and 2675 Ma and a younger suite was emplaced between approximately 2675 and 2611 Ma. Granitoid plutons crystallized at approximately 2611 Ma and cut all the other Archean rocks in the Saddleback greenstone belt.Regional upper greenschist facies metamorphism accompanied the earliest phase of ductile deformation (D 1 ). Sericite-quartz + or - arsenopyrite-altered shear zones developed during subsequent ductile deformation (D 2 ). Crosscutting relationships indicate that D 1 and D 2 predate approximately 2675 Ma. Further ductile shear zones characterized by quartz-albite-sericite + or - pyrite alteration developed during D 3 , after approximately 2675 Ma. Narrow brittle faults (D 4 ) with biotite + or - clinozoisite alteration halos, active between approximately 2675 and 2611 Ma, cut the three generations of ductile shear zones.Rare quartz-albite-fluorite-molybdenite + or - chalcopyrite + or - pyrrhotite veins developed prior to D 1 and the regional metamorphism. These veins are not associated with any Au mineralization or significant Cu. Quartz + or - pyrite + or - molybdenite + or - Au veins and crosscutting clinozoisite-biotite + or - actinolite + or - quartz-chalcopyrite-pyrrhotite + or - galena + or - molybdenite + or - scheelite Au veins developed during movement on the D 4 faults between approximately 2675 and 2611 Ma. Mineralized veins crosscut the three generations of ductile shear zones but are not foliated. Movement on the D 4 faults controlled the location of mineralization within the Boddington gold mine. Higher grade mineralization occurs along the D 4 faults and coplanar pyroxenite dikes and where the faults intersect older shear zones, and quartz veins. Widespread lower grade stockwork mineralization is concentrated in the general vicinity of the D 4 faults. The orientation of veins within stockworks is consistent with vein development during sinistral strike-slip movement on the D 4 faults. Au-Cu + or - Mo + or - W mineralization at the Boddington gold mine, therefore, occurred late in the tectonic evolution of the Saddleback greenstone belt.The timing of mineralization at the Boddington gold mine is analogous to many other structurally late Au deposits in the Yilgarn craton, e.g., Mount Magnet, Mount Charlotte, and Wiluna. Movement on the D 4 faults and mineralization may have been coeval with the emplacement of granitoid intrusions at approximately 2611 Ma. Whereas these granitoids are unaltered and therefore unlikely to have been the source of significant volumes of hydrothermal fluids, they may have provided the thermal energy necessary to drive circulation of auriferous hydrothermal fluids through D 4 faults that may also have accommodated their intrusion.Previous workers at the Boddington gold mine have inferred that mineralization is genetically linked to subvolcanic intrusions emplaced between approximately 2714 and 2696 Ma. However, this inference is inconsistent with the crosscutting relationships of structures and mineralized veins which indicate that mineralization occurred between approximately 30 and 80 Ma after emplacement of these rocks.
|General Geological Map of Boddington Gold Mine|
Batu Hijau Gold Mine
|Batu Hijau Gold Mine|
Location: Sumbawa, West Nusa Tenggara, Indonesia.
Products: Copper & Gold.
Owner: P.T. Newmont Nusa Tenggara.
Ore Type: Porphory Copper deposits.
Reserves: the Batu Hijau included 2.77 million tonnes of copper with an average grade of 0.69g/t gold, which would allow mining to continue until 2025.
Ore geology and Mineralization: The Batu Hijau porphyry Cu‐Au deposit is a world‐class island arc type porphyry deposit, located on the southwestern portion of Sumbawa Island, Nusa Tenggara Barat Province, Indonesia. This 12 km by 6 km district contains an estimated 914 million tonnes of ore at an average grade of 0.53% Cu and 0.40 g/t Au (Garwin, 2002; Arif and Baker, 2004), and is one of the largest and richest porphyry Cu‐Au deposits in Asia.
Ore fluids produced distinct quartz ± sulfide veins and veinlets that cross cut the tonalite intrusions and their surrounding host rocks. Within these veins, fluid inclusions trapped in quartz contain ore fluids, which represent fluids moving through the deposit during the time of its formation. The ore fluids in the fluid inclusions are key to defining the temperature and pressure conditions under which the deposit formed, and defining the geochemistry of the hydrothermal system, which was responsible for the distribution Cu and Au within the deposit.
Preliminary fluid inclusion studies have suggested that deposit formation temperatures ranged from 280 to over 700 °C. Based on the coexistence of magnetite‐bornite ,chalcocite, Garwin (2000) suggested that the earliest veins at Batu Hijau likely formed at > 500–700 °C (cf. Simon et al., 2000). A preliminary fluid inclusion study by Garwin (2000) on inclusions in halite‐bearing transitional veins produced homogenization temperatures that ranged from about 450 to 500 °C. These temperatures are consistent with phase equilibria temperature estimates based on a chalcopyrite , bornite vein mineralogy (Simon et al., 2000).
Homogenization temperatures of < 400 °C were obtained by Garwin (2000) for late pyrite‐bearing veins. A fluid inclusion study conducted by Imai and Ohno (2005) documented homogenization temperatures ranging from 280 to 454 °C, significantly lower than temperatures obtained by Garwin (2000). This temperature is similar to Au saturation temperatures for bornite (~300 °C) and chalcopyrite (250 °C) (Kesler et al., 2002; Arif & Baker, 2004).
A detailed fluid inclusion microthermometry study to clarify processes of ore formation is warranted. Microthermometric data on well‐characterized fluid inclusions with appropriate pressure corrections can provide the temperatures and pressures at which the deposit formed. Additional qualitative and quantitative data from synchrotron x‐ray fluorescence (SXRF) and laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS), respectively, can document and quantify major and trace element concentrations. Such data will contribute to a model describing the transport of metals by hydrothermal fluids, and the precipitation of Cu‐ and Au‐bearing minerals.
Mining & Milling: Batu Hijau is an open-pit mine. Ore is removed from the mining face using P&H 4100 electric shovels (pictured) and loaded into Caterpillar 793C haul trucks. Each haul truck can move a payload 220 t (240 short tons) of ore. The trucks haul ore from the shovel to primary crushers. Crushed ore is sent by a conveyor 1.8 m (6 ft) wide and 6.8 km (4.2 mi) long to the mill. Daily production from the mine is an average of 600,000 t (660,000 short tons) ore and waste combined. Ore from the mine has an average copper grade of 0.49% and an average gold grade of 0.39g/t.
Crushed ore is further reduced in size by Semi-Autogenous Grinding and ball mills. Once milled it is sent through a flotation circuit which produces a concentrate with a grade of 32% copper and 19.9g/t gold. The mill realizes a copper recovery of 89%. The concentrate is thickened into slurry and piped 17.6 km (10.9 mi) to the port at Benete where water is removed from the slurry. The concentrate storage at the port can hold 80,000 t (88,000 short tons) of copper-gold concentrate.
The Herradura Gold Mine
|La Herradura Gold Mine .|
Location: Sonora, Puerto Penasco, Mexico (MX).
Owner: Fresnillo plc.
Average ore grade in reserves: 0.80 g/t Gold
Total Reserves: 1.5 Moz Gold
Mine Life: 4.1 years
MINING AND EXPLORATION HISTORY
The La Herradura mine contains 5.4 million ounces of contained gold in production plus reserves. The deposit is owned by Minera Penmont, a Joint Venture between Peñoles and Newmont. As a result of an aggressive grassroot exploration program in northwestern Mexico that started in 1987, the first economic drill intersection in La Herradura came in 1991 (100m @ 0.85 g/t Au). Subsequent and continuous drilling campaigns resulted in the definition of an orebody containing 1.7 M oz by May 1998, when mine operations started. To date, 2 M oz of gold have been produced. Present reserves are 3.4 M oz of gold in ore with an average grade of 1 g/t, using a cut-off of 0.35 g/t Au. The mine produces 210,000 ounces of gold per year ( Jose de la Torre, pers. commun., 2008).
Regional Geologic and Tectonic Setting
La Herradura mine is located in northwestern Sonora, Mexico. This deposit occurs within a northwest trending belt that consists of metamorphic rocks of greenschist and amphibolite facies and granitoids of Proterozoic age (Nourse et al., 2005). These rocks are intruded by a series of Triassic and Middle Jurassic granitoids and are overlain by younger sedimentary and volcanic rocks of Middle to Late Jurassic age (Figure 2.1). All these units are intruded by Late Cretaceous to early Tertiary granitoids related to the Laramide orogeny and are overlain by Miocene rhyolites, andesites, and basalts and Quaternary basalts. Basin and Range tectonics affect this area, as they do much of Sonora and adjacent Arizona. Basin and Range faulting occurred in the mid to late Tertiary. Faulting resulted in the formation of NW-trending linear ranges of crystalline rock, separated by deep basins filled with sand and gravel derived from the ranges. Correlation is difficult between ranges.
The Geologic Setting of La Herradura
La Herradura mine occurs within a northwest trending belt of Proterozoic rocks consisting of greenschist and amphibolite grade metamorphic rocks and granitoids. The deposit is hosted in biotite-quartz-feldspar and quartz-feldspathic gneisses that are bordered to the east by Jurassic clastic rocks and subvolcanic intrusions and to the west by upper Paleozoic limestone. Isolated outcrops of fresh andesite, trachyte, and basalt occur locally northeast of the mine.
The Structural Setting of La Herradura
Based on structural mapping in the La Herradura mine area, it is possible to identify at least five tectonics events superimposed on all stratigraphic units outcropping in this area (de la Torre, 2004; Romero 2005, Table 2.1). These observations indicate that gold mineralization is associated with the third tectonic event, and they also tend to constrain the age of this mineralization to between 80 and 45 Ma.
Alteration of La Herradura
Reported alterations assemblages of this deposit (de la Torre, 2004; Romero, 2005) are quartz-sericite-albite in the core of the deposit and selectively follow the quartz-feldspar gneiss bands in the outer zones of the deposit. Iron-carbonates (ankerite-siderite) are widespread within the deposit, mainly restricted to haloes adjacent to quartz-sulfide veins within the core of the orebody. Iron carbonates also are found in the outer alteration aureoles of the deposits. Propylitic alteration islocated in the outermost portions of the deposit, and it occurs mainly in the biotite-bearing gneiss and in Jurassic rhyolitic and andesitic volcanic rocks.
Location: Elqui, Coquimbo, Chile.
Products: Copper & Gold.
Owner: Royal Gold,Inc.
Ore Type: Porphyry copper-gold deposit, hosted by altered andesitic and dacitic volcanic rocks, and small stocks and irregular dykes of potassium-rich tonalitic porphyry.
The Andacollo mining district is located in the Coquimbo region of Chile at 30°14’ south, 71°06’ west, some 55 km southeast of La Serena, at a mean elevation of 1030 m within a semi-arid hilly landscape. Current mining activity in the district is concentrated on copper and gold. These metals are mined, respectively, from a porphyry copper deposit and epithermal, manto and vein gold deposits of adularia–sericite type.11,13 Other types of mineralization include mercury veins hosted by carbonate rocks. The gold veins are controlled by a northwest-trending set of normal faults, whereas the manto-type mineralization is strata-bound and largely confined to andesite breccias, dacites and sites of strong fracturing. The lateral and vertical continuity of the mantos is strongly controlled by rock type, faulting and intensity of fracturing. The gold deposits have been the focus of a recent study,11 but comparable information on the Andacollo porphyry has not become available.
Andacollo’s operating profit from August 22 to December 31, 2007 was $27 million before the effects of the revaluation of copper inventory to fair value on acquisition and negative pricing adjustments. The revaluation established a higher value for copper inventories, based on market prices at the date of acquisition. This increased our cost of sales by $24 million and the subsequent decline in metal prices resulted in a loss on the sale of these inventories. In addition, the mine recorded negative pricing adjustments of $2 million since they acquired it in August 2007. After these adjustments, Andacollo’s operating profit was $1 million. Copper cathode production in 2008 is expected to be approximately 20,000 tonnes and capital expenditures are planned at US$190 million, including US$185 million on the hypogene development.
Geological setting and Mineralization
The Andacollo deposits are the products of a complex hydrothermal system and consist of a porphyry copper-gold deposit and peripheral strata-bound manto gold deposits and veins with minor associated base metals. The hydrothermal system was part of the Pacific porphyry copper belt which was generated during development of an Early Cretaceous magmatic arc displaying shoshonitic petrochemical affiliations. Rocks that crop out in the area include a volcanic sequence, the Arqueros and Quebrada Marquesa Formations, consisting of andesitc and dacite flows, volcanic breccias, and pyroclastic rocks of Early Cretaceous age. Intrusive rocks range from diorite to granodiorite in composition and date between 87 and 130 Ma. The porphyry copper-gold deposit is zoned vertically downward from a leached capping through a supergene enrichment blanket to a hypogene sulfide zone. Alteration is characterized by central potassic (K feldspar-biotite), phyllic, and peripheral propylitic zones. Abundant northwest-trending tensional fractures were superimposed on the porphyry copper-gold deposit and surrounding areas during the later stages of the evolving mineralized system. The fractures channeled mineralizing fluids from the central parts of the porphyry copper deposit outward for up to 5 km. Replacement by adularia and sericite took place together with deposition of gold-bearing pyrite and minor amounts of zinc and copper where these fluids encountered permeable dacite flows and andesite flow breccias. The alteration process caused remobilization of aluminum and alkalies and addition of K 2 O, which attains values of 12 to 13 wt percent. The Andacollo system is interpreted to be a porphyry copper-gold deposit that is transitional outward to distal epithermal, adularia-sericite-type contact metasomatic gold orebodies.